The acting chief of the Federal Aviation Administration defended his agency's safety certification of the Boeing 737 Max jetliner, the plane involved in two deadly crashes, and the FAA's decision not to ground the jet until other regulators around the world had already done so.

During a congressional hearing Wednesday, the FAA official, Daniel Elwell, also stood by the agency's decades-old policy of using employees of aircraft manufacturers like Boeing to conduct inspections on their own companies' work.

Boeing is updating an automated flight-control system that has been implicated in the two crashes involving the 737 Max. Elwell said he expects Boeing to complete its work "in the next week or so," after which the FAA will analyze the software changes and conduct test flights.

"In the U.S., the 737 Max will return to service only when the FAA's analysis of the facts and technical data indicate that it is safe to do so," Elwell said.

Meanwhile, the Senate Commerce Committee held a short hearing for President Donald Trump's choice to take over the FAA: Stephen Dickson, a former Delta Air Lines pilot and executive.

During the two-hour questioning of Elwell by the House aviation subcommittee, lawmakers pressed him on the FAA's reliance on designated Boeing employees during the planes' certification process.

Rep. Dina Titus, D-Nev., told Elwell that the public believes "you were in bed with those you were supposed to be regulating, and that's why it took so long" to ground the planes.

"The FAA has a credibility problem," declared the subcommittee chairman, Rick Larsen, D-Wash.

The 737 Max is Boeing's best-selling plane and it is built in his home state of Washington. Larsen said Congress must help make the public feel safe about flying because "if they don't fly, airlines don't need to buy airplanes," and "then there will be no jobs" in aircraft manufacturing.

Other lawmakers defended the FAA and Boeing and suggested that the Oct. 29 crash of a Lion Air jet off Indonesia and the March 10 crash of an Ethiopian Airlines Max were due at least partly to pilot error. A total of 346 people were killed in the crashes.

"It bothers me that we continue to tear down our system based on what has happened in two other countries," said Rep. Sam Graves, R-Mo.

Boeing is already the subject of a criminal investigation by the Justice Department. Boeing customers Southwest Airlines and American Airlines and their pilot unions have received subpoenas related to that investigation; United Airlines, which also flew the Max until it was grounded in March, declined to comment, although its pilot union confirmed that it too has received a subpoena.

Congressional investigations into the FAA's relationship with Boeing are in the early stages. Rep. Peter DeFazio, D-Ore., who heads the full Transportation Committee, said he and Larsen have been frustrated after seeking information from Boeing.

"Boeing has yet to provide a single document," he said. "We've got to get to the bottom of this."

Elwell defended FAA's practice of designating employees of Boeing and other aerospace manufacturers to do some inspection work, saying it takes advantage of industry expertise, and "when done right, is indispensable to the health and safety of our system."

At a Senate hearing in March, Elwell said it would cost $1.8 billion a year if FAA did all the work done by designees at companies regulated by the agency.

On Wednesday, the acting chief defended the FAA's 2017 approval of the Max including its new automated flight-control system that can push the nose of the plane down if a single sensor detects that the plane could be nearing an aerodynamic stall.

That system, called MCAS, was triggered on both fatal flights by faulty sensor readings, and pilots were not able to regain control of the planes as they plunged to Earth. Airlines and pilots were not told about MCAS until after the October crash.

"When I first heard of this, (I) thought that the MCAS should have been more adequately explained in the ops manual and the flight manual," Elwell said.

Boeing is changing MCAS to make it less powerful, and to link the system to two sensors instead of one. And it will include more explanation of the system, Elwell said, "to make pilots more aware and respond better to an anomaly."

American Airlines pilots pressed Boeing in November — shortly after the first Max crash — to fix the software quickly.

"We don't want to rush and do a crappy job of fixing things," a Boeing official responded, according to a recording of the meeting. "We also don't want to fix the wrong things."

The Boeing representative called the Lion Air crash a tragedy, adding, "an even worse thing would be another one." He promised a software update in six weeks.

The update was still not done when the Ethiopian crash occurred more than three months later.

"Boeing did not treat the 737 Max 8 situation like the emergency it was," said Daniel Carey, president of the American Airlines pilots' union, which has filed public records related to the matter. Carey said his pilots are seeking "proper oversight" of Boeing, the FAA and airlines including their own.

Boeing representatives were not invited to Wednesday's hearing.

Nadia Milleron, whose daughter, Samya Stumo, was on the Ethiopian Airlines plane, was in the audience. She said FAA seems to be rushing to approve Boeing's fixes to the Max even before the accident investigations are finished — something that could take many months.

"It is possible that these planes should never go back in the air," she said.

Milleron, whose family is suing Boeing and Ethiopian Airlines, said travelers hold the final power to ground the plane.

"The only thing that is going to stop this is the public," Milleron said in an interview. "If the public is concerned and if the Boeing 737 Max 8 ... becomes toxic ... that's going to make a change."

Across Capitol Hill, the Senate Commerce Committee held a relatively placid hearing for Dickson, the nominee to replace Elwell, FAA's acting administrator since January 2018.

Dickson promised that if he is confirmed by the full Senate, he would not hesitate to take enforcement action against companies and FAA would not be captive to the industry it regulates.

U.S. aviation has an enviable safety record over the past decade, Dickson said, but the industry is only as good as the last takeoff or landing.

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Koenig reported from Dallas, Krisher from Detroit.

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